1. Scope of the Invention
This invention relates principally to the field of secure computers, and more particularly to apparatus for assuring that commodity controllers do not communicate directly with a secure memory.
2. Description of the Prior Art
Many personal computers are made up of commercially available commodity boards. These boards include a base processor board, memory commodity boards and controller commodity boards, all coupled together by a common bus. The common bus includes address lines and data lines. Any commodity board may write into and read from the memory in competition with each other. This presented problems since under some conditions, mostly malfunctioning conditions, data would be lost due to overwriting.
To prevent this condition, an I/0 processor was placed between the commodity controller and commodity memory. This alleviated the problem somewhat, however since the commodity controller could bypass the I/0 processor and write into or read from memory directly, the management of memory became difficult. This presents particular problems when a secure computer operates with commercially available commodity controller boards and commodity memory boards.